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Re: Recent s.s.t.c. work
Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>
"Gates" always blew a little above 50V when I used to destroy things
specifically testing for that... And I tested thousands... They all
make the gate oxide layers the same...
But a transorb directly from gate to source (gate to emitter ;-)))
will fix that problem right there without any worry. Unless you try
something really odd, the dV/dT will never be high enough to get past
the transorb. 30V is a nice voltage for them, That gives 20V of
margin for them to kick in if something really fast comes along. A
gate drive voltage of 25 volts should turn on a device to the point
where more voltage just does not matter any more. Thus, I drive to
25V and protect at 30V...
The spec of 15 or 20V for gate drive just is not quite enough for
"us" ;-))) But past 25V, the silicon just gives up and more voltage
is just waisted in gate capacitance charging energy...
At 03:39 PM 11/29/2005, you wrote:
I'd be hesitant to come to that conclusion. IGBT gates can go pretty
freaking high before they fail (I have tested mine to 50v, and
remember an application not saying 50% survival was at 70-80v!), and
the gate shorts out when the CE is overvolted, or the device
overheats as well. How high were you running the gate voltage?
It can be frustrating when you think you fixed a problem, and it
happens again. You don't want to lose any more motivation!
On 11/29/05, Tesla list <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx> wrote:
Original poster: "K. C. Herrick" <<mailto:kchdlh@xxxxxxx>kchdlh@xxxxxxx>
Just to assure some of you that I've not totally given up yet...
As I've mentioned before, I find that at my advanced age I'm losing
the motivation to continue "making things"--as I have been doing for
~70 years. So I haven't done anything further yet on trying to find
the source of the problem with my new s.s.t.c. I think that I have
set the peak gate voltage too high, and consequently shorted the gate
of one of the bricks. I can readily reduce that by 5V and I have 2
more good bricks; it's just a matter of getting around to it.
Finn Hammer mentioned potential problems with putting the primary
inside the secondary, as I have done. I think my solution to that
would be to raise up the entire secondary so that the bottom of it
was more or less at the top of the primary winding. Then, add an
auxiliary secondary, of sufficiently larger diameter, aligned with
the primary and of more or less the same height. That way, I keep
all the existing hardware and only have to fabricate the relatively
simple auxiliary coil and its former.
So the steps I need to take are clear. I'll likely get to them some
time after the holdiays are over.